Near-field light generating method and near-field optical head using a light blocking metal film having a fine opening whose size is not more than a wavelength of irradiated light, and near-field optical microscope having the optical head

ABSTRACT

A near-field light generating method for irradiating light from a light source to a metal film having a fine opening that has a size of not more than a wavelength of the light emitted from the light source, and forming a fine light spot adjacent to the fine opening on a light outgoing side of the fine opening. The method includes providing the metal film with a rectangular fine opening whose length to width ratio is between 1.1 times and 2 times that of a standard square opening, obtained by increasing the length of the standard square opening, and irradiating the metal film with light from the light source to form the fine light spot, which has a length and a width that are substantially equal to those of the standard square opening, and where the fine light spot has a light intensity, which is not less than two times that of the standard square opening. This method is applicable in a corresponding near-field optical head, which can be included either in an optical microscope to observe a sample surface or in an apparatus for recording and reproducing with respect to a recording medium.

This application is a U.S. national stage application of PCTInternational Application No. PCT/JP2004/014445, filed Sep. 24, 2004,and which claims priority from Japanese patent application number2003-334610, filed Sep. 26, 2003, both of which are incorporated byreference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a near-field light generating method, anear-field exposure mask, a near-field exposure method, a near-fieldexposure apparatus, a near-field optical head, a near-field opticalmicroscope, and a recording and reproducing apparatus.

PRIOR ART

The increasing capacity of a semiconductor memory and the increasingspeed and density of a CPU processor have inevitably necessitatedfurther improvements in the fineness of microprocessing through opticallithography. Generally, the limit of microprocessing with an opticallithographic apparatus is on an order of the wavelength light beingused. Thus, the wavelength of light used in optical lithographicapparatuses has been shortened more and more. Currently, a nearultraviolet laser is used, and microprocessing on an order of 0.1 μm isenabled. While the fineness is being improved in the opticallithography, in order to assure microprocessing on an order of 0.1 μm ornarrower, there still remain many unsolved problems, such as furthershortening of the wavelength of laser light, development of lensesusable in such a wavelength region, and the like.

On the other hand, as a means for enabling microprocessing on an orderof 0.1 μm or narrower, a microprocessing apparatus using a principle ofa near-field optical microscope (scanning near-field optical microscope:SNOM), has been proposed. For example, an exposure method has beenproposed in which, by use of near-field light leaking from a fine slitof a size not greater than 100 nm, local exposure that exceeds the lightwavelength limit is performed to a resist.

As a means for such a purpose, a method of performing microprocessingsis utilized, in which a near-field probe is provided and a near field isgenerated by localized plasmon generated in a metal pattern, to effectmicroprocessing. In this method, however, microprocessing is performedwith one or more processing probes, as in unicursal drawing, so that thethroughput is not necessarily improved satisfactorily.

As another method, Japanese Laid-Open patent Application (JP-A) No. Hei08-179493 has proposed a method such that a photomask with a fineopening pattern, having a size of not more than a wavelength of light,is provided with a prism, the light is caused to enter the photomask atan angle causing total reflection, and a pattern of the photomask issimultaneously transferred to a resist by use of evanescent lightleaking from the total reflection surface.

Further, U.S. Pat. No. 6,171,730 discloses such an exposure techniquethat a photomask, including a light blocking film having an openingpattern of not more than 0.1 μm, is irradiated with light from its backside and by use of near-field light leaking from the opening pattern, sothat the pattern of the photomask is simultaneously transferred to aresist.

However, with respect to the above-described methods in which thenear-field light is generated by use of the photomask having a fineopening pattern, a further improvement in generation efficiency ofnear-field light and generation of higher intensity near-field light aredesired.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a near-field lightgenerating method and a near-field exposure mask, which permit ahigher-efficiency generation of more intense near-field light.

Another object of the present invention is to provide a near-fieldexposure method and apparatus and a near-field light optical head, whichutilizes the above method or the mask.

A further object of the present invention is to provide a near-fieldoptical microscope and a recording and reproducing apparatus, which usethe near-field optical head.

According to the present invention, a near-field light generating methodis provided for forming a fine light spot at a portion adjacent to afine opening having a size of not more than a wavelength of light on alight outgoing side of the fine opening by irradiating the fine openingwith the light, the method comprising:

forming a light spot having a length and a width which are substantiallyequal to each other by the fine opening, the fine opening having arectangular shape having a length and a width which are different fromeach other.

In the above-near-field light generating method, the length and thewidth of the light spot may be determined by the width of therectangular opening.

In the near-field generating method, the fine opening may be provided ina plurality of fine openings including the rectangular opening and aslit-like opening.

According to the present invention, a near-field exposure mask comprises

a mask base material,

a light blocking layer disposed on the mask base material, and

a fine opening having a size of not more than a wavelength of light usedfor exposure,

wherein the fine opening comprises a rectangular opening having a lengthand a width which are different from each other, the rectangular openinghaving a length/width ratio which permits transfer of a pattern having alength and a width which are substantially equal to each other.

In the near-field exposure mask, the fine opening is provided in aplurality of fine openings including the rectangular opening and aslit-like opening. Further, the fine opening has a length/width ratio of1.1 to 2.

According to the present invention, a near-field exposure methodcomprises providing the near-field exposure mask described above, andexposing an exposure object to light by using the near-field exposuremask.

According to the present invention, a near-field exposure apparatus, forexposing an exposure object to light, comprises the near-field exposuremask described above, and a light source to be exposed to light.

According to the present invention, a near-field optical head comprises:

means for generating near-field light, provided with a rectangular fineopening having a size of not more than a wavelength of light or acombination of the rectangular fine opening and a slit-like opening,

wherein a light spot, having a length and a width, which aresubstantially equal to each other by the rectangular fine opening, isformed at a portion adjacent to an opening portion on a light outgoingside of the rectangular fine opening.

According to the present invention, a near-field optical microscope, foreffecting surface observation of a sample, comprises a near-fieldoptical head as described above.

According to the present invention, a recording and reproducingapparatus, for effecting recording and reproduction with respect to arecording medium, comprises the near-field optical head described above.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a structure of a near-field exposurephotomask according to an Embodiment of the present invention.

FIGS. 2A and 2B are schematic views showing analysis results ofnear-field light by the near-field exposure photomask, wherein FIG. 2Ashows a near-field distribution in the neighborhood of a rectangularopening in the Embodiment of the present invention and FIG. 2B shows anear-field distribution in the neighborhood of a square opening as acomparative Embodiment.

FIG. 3 is a schematic view showing a structure of a near-field exposureapparatus in Embodiment 1 of the present invention.

FIGS. 4A to 4D are schematic views for illustrating a method ofmanufacturing a near-field exposure photomask in Embodiment 1 of thepresent invention.

FIGS. 5A to 5D are schematic views for illustrating a method of forminga pattern including a single buffer layer by use of the near-fieldexposure photomask in Embodiment 1 of the present invention.

FIG. 6 is a schematic view showing a structure of a near-field opticalhead in Embodiment 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is characterized in that in a near-field lightgenerating method, a higher intensity near-field light is obtained byusing a rectangular opening having a length (long side) and a width(short side), which are different from each other (herein, simplyreferred to as a “rectangular opening”).

The present invention will now be described with reference to thedrawings.

FIG. 1 shows a structure of a near-field exposure mask (photomask)according to an embodiment of the present invention.

In FIG. 1, the near-field exposure mask includes a mask base material101, which is transparent to a wavelength of a light source, a metalfilm 102 having a thickness t disposed thereon, a substrate 103 forsupporting the mask base material 101, a rectangular fine openingpattern 104, disposed in the metal film 102, having a size of not morethan the wavelength, and a slit-like fine opening having a width of notmore than the wavelength. The mask base material comprises a 0.1-100 μmthick film and is supported on the substrate 103.

The photomask is, as described later, caused to closely contact a thinfilm resist applied onto a substrate, and is irradiated with light fromthe mask base material side to be used for pattern exposure.

A description of near-field light by the rectangular fine opening,provided in the photomask described above, will now be explained, on thebasis of an analysis result according to a finite difference time domainmethod.

In the analysis, a calculation is performed on the precondition that amask, comprising an SiN layer and a 50 nm-thick Cr film disposedthereon, is placed in such a state that it closely contacts asufficiently thick photoresist. A wavelength of light from a lightsource is 436 nm (g line as an emission line of Hg) in a vacuum. Thecalculation results are shown with respect to two polarizationdirections perpendicular to each other and are obtained, respectively,by adding an independently calculated result of light intensity. Themask used comprises a light blocking film of Cr provided with a fineopening.

FIG. 2A shows a near-field distribution in the neighborhood of therectangular opening having a size of 40 nm (width)×60 nm (length).

In FIG. 2A, a solid line represents an iso-intensity line of anintensity of 0.3 in the case when an intensity of incident light istaken as 1. As shown in FIG. 2A, at a depth of 20 nm in the resist, itis found that the near-field distribution has an exposure of 50 nm inthe x direction and 40 nm in the y direction. Further, a dashed linerepresents an iso-intensity line of an intensity of 0.3 in a near-fielddistribution at a cross section of a 40 nm-wide slit-like opening (longslit), which is disposed together with the fine opening.

FIG. 2B shows, as a comparative embodiment, a near-field distribution inthe neighborhood of a square opening having a size of 40 nm×40 nm.

The near-field in the neighborhood of the square opening has anintensity lower than that in the neighborhood of the rectangularopening. Accordingly, in this embodiment, a solid line represents aniso-intensity line having an intensity of 0.15 in the case of anincident light intensity of 1. The iso-intensity line shows that theintensity of the incident light is to such an extent that the incidentlight reaches a depth of 25 nm. It is found that the resultant spot hasa size of 50 nm×50 nm at a depth of 20 nm. Further, a dashed linerepresents an iso-intensity line having an intensity of 0.15 in anear-field distribution at a cross section of a 40 nm-wide slit-likeopening (long slit) disposed together with the fine opening, and shows aprofile which extends in a direction along the mask surface.

From the above results of calculation, the following points have beenfound.

One is that a distribution intensity of near-field light in theneighborhood of the rectangular fine opening is higher than that of thesquare fine opening.

In the case when an exposure condition is selected on the basis offormation of a latent image, having a desired size, which reaches adepth of 20 nm of the resist and the rectangular opening is used withrespect to the resist, it is found that an exposure time may bedetermined, so that the iso-intensity line having an intensity of 0.3provides a limit of solubility/insolubility of the resist. Further, byeffecting the exposure for such an exposure time, an 80 nm-wise linepattern can be formed in a depth of 20 nm, even when the slit-like fineopening is used. In order to provide a line pattern having a widthsubstantially equal to that of a spot, the width of the slit-like fineopening may be further narrowed. More specifically, when a slit-likeopening is formed with a width of 30 nm, a line pattern with a width of50 nm can be formed in a depth of 20 nm in the resist.

On the other hand, in the case when the photomask having a squareopening is used, the distribution intensity of near-field light is low.For this reason, in order to form the latent image, which reaches thedepth of 20 Dm similarly, as in the above-described case, it isnecessary to effect exposure for such a time that the iso-intensity lineof an intensity of 0.15 provides a limit of solubility/insolubility ofthe resist. In other words, it is necessary to take an exposure timesubstantially two times that in the case of the rectangular opening.Further, when the same exposure condition is applied to the slit-likepattern, the resultant line pattern is subjected to excessive exposure.As a result, it is difficult to form a desired line pattern (FIG. 2B).

In this embodiment, the results described above are based on onecalculation example, but a similar tendency is shown with respect to anopening having a size of not more than the wavelength of light. When therectangular opening having a length and a width, which are differentfrom each other, is used, it becomes possible to obtain near-field lighthaving a higher intensity than the case of using the square opening.This is because, as one of a length and a width of the square opening isgradually increased to change the length and the width of the squareopening, an intensity of near-field light leaking from the resultantopening becomes abruptly higher. More specifically, a degree ofattribution of a vector component, parallel to the short side (width) ofelectrical field vectors directed in two polarization directions, isprincipally increased. However, light of such a polarization componentis directed so that an electrical field in the neighborhood of the shortside of the rectangular opening is parallel to an interface. As aresult, an intensity of a near-field immediately in the neighborhood ofthe short side does not become higher. That is, when the shape of theopening is changed from a square to a rectangle, the opening isparticularly irradiated with a polarized component of light, and anelectrical field vector, which is parallel to the short side of theopening, is thereby generated, to immediately increase an intensity oflight leaking from the opening. On the other hand, a degree of expansionof near-field light by such a polarized component is moderate, so thatit becomes possible to obtain a higher-intensity near-field light whenthe rectangular opening having a length and a width, which are differentfrom each other, is used.

In the case when the above-described phenomenon is used for near-fieldexposure, it is possible to set an exposure condition such that ahigher-intensity iso-intensity line provides the limit ofsolubility/insolubility of the resist. For example, in the case ofassuming a certain exposure condition which permits formation of alatent image having a desired size in a desired depth of the resist,with respect to a standard square opening, one of adjacent sides of theopening is increased to provide a rectangular opening. As a result, theintensity of near-field light can be increased. In this case, it is notnecessary to effect polarization control of light with respect to thelight source. When the intensity of near-field light becomes higher, itis possible to provide an equivalent amount of exposure light byeffecting exposure in a shorter time. As an iso-intensity line (e.g., anintensity I0) being a measure of latent image formation, a newiso-intensity line having a higher intensity (e.g., an intensity I1(e.g., I1=2×I0)), compared with the case of the square opening, is used.The iso-intensity line of intensity I0 becomes broader with an increasein a long side of the rectangular opening, but the new iso-intensityline of an intensity I1 may be used for exposure. As a result, itbecomes possible to effect exposure in a short time without causing aremarkable increase in latent image size.

In view of the calculation results, a ratio of length to width(length/width ratio) of the rectangular opening for use with exposure,in accordance with the above-described mechanism, may appropriately beabout 1.5. Further, in order to significantly enhance the lightintensity as compared with the case of a square opening, thelength/width ratio is required to be at least 1.1 times that of thesquare opening.

On the other hand, in order to provide a length/width ratiosubstantially equal to that of the square opening (e.g., not more than1.1 times that (=1) of the square opening), when a fine light spot isformed by use of the rectangular opening in the neighborhood of the fineopening at an opening portion on the light incident side, it isnecessary to provide the fine opening with the length/width ratio, whichis two times that of the square opening. In other words, in the presentinvention, the fine opening may preferably have a length/width ratio of1.1 to 2. As described above, when the rectangular opening is used withreference to the results of the analysis of the electromagnetic field,it is possible to obtain a light intensity, which is not less than twotimes that of the square opening. As a result, it is found that itbecomes possible to reduce the exposure time required for forming thelatent image, which reaches the same depth in the resist. Further, asshown in FIG. 1, when the photomask has the rectangular opening and theslit-like opening in combination, it is found that both patterns of therectangular opening and the slit-like opening can be used for patterningunder the same exposure condition.

Embodiments of the present invention will now be described morespecifically.

Embodiment 1

FIG. 3 shows a structure of a near-field exposure apparatus inEmbodiment 1 of the present invention.

In the near-field exposure apparatus, a near-field exposure mask 301 isprovided with a fine opening pattern, in combination with a slit-likeline pattern, which has a length larger than a wavelength of light. Thenear-field exposure mask 301 has patterns in a light blocking filmformed on an elastic mask base material. Herein, a “front surface” ofthe mask refers to a surface where the light blocking film (for themask) is disposed, and a “rear surface” refers to a surface oppositefrom the front surface.

In this embodiment, the front surface of the photomask 301 is disposedapart from a pressure adjusting (regulating) vessel 305 and the rearsurface is disposed to face the pressure adjusting vessel 305. Thepressure adjusting vessel 305 is designed to permit adjustment ofpressure therein by a pressure adjusting means 313.

A member to be exposed comprises a substrate 306 and a resist film 307disposed on the surface of the substrate 306 (hereinafter referred to asthe “resist 307/substrate 306”).

The resist 307/substrate 306 is mounted on a stage 308 and the stage isdriven to effect relative positional alignment of the substrate 306 withthe photomask 301 in a two-dimensional direction with respect to themask surface.

Next, the stage 308 is moved in a direction of a normal to the masksurface, to bring the photomask 301 into close contact with the resist307 disposed on the substrate 306.

During the close contact operation, the pressure in the pressureadjusting vessel 305 is adjusted by the pressure adjusting means 313, sothat a distance between the entire front surface of the photomask 301for evanescent light and the resist 307 disposed on the substrate 306becomes not more than 100 nm. Thereafter, exposure light emitted from anexposure light source 309 is changed to parallel light by a collimatorlens 311, and passed through a glass window 312, to be introduced intothe pressure adjusting vessel 305. The evanescent light exposure mask(photomask) 301 is irradiated with the light from its rear surface side.At that time, exposure of the resist 307 is performed by near-fieldlight generated adjacent to the fine opening at the front surface of thephotomask 301.

The mask pattern includes, as shown in FIG. 1, independent rectangularopenings and a slit-like line pattern, having a length larger than thewavelength of light, in combination with the independent rectangularopenings. Each of the rectangular openings has a width (short side) of40 nm and a length (long side) of 60 nm, and the slit-like line patternhas a width of 30 nm.

A method of manufacturing the near-field exposure mask in thisembodiment will be described in detail with reference to FIGS. 4A to 4D.

As shown in FIG. 4A, on a 500 μm-thick double-sided polished substrate401 of Si (Si (100) substrate 401), a 0.8 μm-thick SiN film 402, as amask base material, is formed at the front surface (an upper surface inFIG. 4A of the substrate 401 by an LP-CVD (low pressure-chemical vapordeposition) method, and a 0.8 μm-thick SiN film 403 as an etching windowis formed at the rear surface (a lower surface in FIG. 4A) by an LP-CVDmethod. Thereafter, on the surface of the SiN film 402, a 70 μm-thick Crfilm 404 is formed by a vapor deposition method, while effecting controlof the film thickness by a film thickness monitor by use of a quartzoscillator.

Then, onto the surface of the Cr film 404, a resist 405 for an electronbeam is applied, and a pattern 407, including a width of 20 nm and awidth of 50 nm, is formed by electron beam 406 (FIG. 4B). Afterdevelopment, the resist 405 is subjected to dry etching with CCl₄ toprovide a fine opening pattern 408 (FIG. 4C).

A part of the SiN film 403 (formed at rear (lower) surface of thesubstrate 401) is removed to form a window 409 for etching (FIG. 4C).Anisotropic etching with a KOH solution is performed from the rear(lower) surface side of the substrate 401 to remove a part of the Sisubstrate 401, to provide a mask 410 principally comprising the SiN film402 and the Cr film 404 (FIG. 4D).

In this embodiment, in the step of forming the fine opening pattern 408in the Cr film 404, the electron beam processing is employed, but otherprocessing methods, such as focused ion beam processing, X-raylithography, and scanning probe microscope (SPM) processing, may beused. Of these processing methods, such a processing that the SPMtechnique represented by a scanning tunnel microscope (STM), an atomicforce microscope (AFM) or a scanning near-field optical microscope(SNOM) is applied thereto, may preferably be used, since it becomespossible to form a very fine opening pattern of not more than 10 nm whenformation of the fine opening pattern is performed by the processing.

Referring gain to FIG. 3, as a material for the resist 307, aphotoresist material used in an ordinary semiconductor process may beselected.

With respect to the resist material, a wavelength of light which permitsexposure is in the range of about 200-500 nm. However, when aphotoresist, which is sensitive to g line and i line of a mercury (Hg)lamp in a wavelength range of 350-450 nm is selected, it becomesdesirable to allow more process latitude and reduction in cost, sincesuch a resist material has a great choice, and is relativelyinexpensive.

The exposure light source 309 is required to emit light having anexposable wavelength with respect to the resist 307 being used. Forexample, when the photoresist for the above-described g line or i line(of Hg) is selected as the resist 307, as the light source 309, thoseincluding HeCd laser (light wavelength: 325 nm, 442 nm), GaN-type bluesemiconductor laser (410 nm), a second or third harmonic generation (SHGor THG) laser of an infrared light laser, and a mercury (Hg) lamp (gline: 436 nm, i line: 365 nm) may be used.

An amount of exposure light is adjusted by controlling a drive voltage,a drive current and an irradiation time of the exposure light source309. In this embodiment, the g line (wavelength: 436 nm) of the Hg lampis used, so that an area of 100 nm×100 nm is irradiated with the g linelight by use of a collimator lens through a wavelength selection filter.A power of the light is monitored by a power meter, and an exposure timeis set so that the light exposure amount of the resist exceeds athreshold with respect to exposure. In this case, it is necessary toadjust the light exposure amount in view of light transmittance of thephotomask as the exposure is performed through the photomask.

FIGS. 5A to 5D are views for illustrating a method of forming a patternincluding one buffer layer by use of the near-field exposure mask inthis embodiment.

FIG. 5A shows a photomask 504 and a member to be exposed to light.

The photomask 504 is a photomask identical to that described above withreference to FIG. 3.

Onto an Si substrate 501, a positive photoresist is applied by use of aspin coater and heated at 120° C. for thirty minutes to form a 400nm-thick first layer 502. Onto the first layer 502, an Si-containingnegative photoresist is applied and pre-baked to form a 20 nm-thicksecond layer 503.

The Si substrate 501, onto which the photoresist having a two-layerstructure is applied, and the photomask 504, are caused to come close toeach other by the near-field exposure apparatus, and pressure is appliedthereto to bring the resist layer 503 and the photomask 504 in closecontact with each other.

The resultant structure is irradiated with exposure light 505 throughthe photomask 504, whereby the pattern on the photomask 504 is exposedto the light, and thus, a portion 506 of the photoresist layer 503 isalso exposed to light (FIG. 5B). Thereafter, the photomask 504 isremoved from the photoresist surface, and the photoresist 503 issubjected to development and post-baking, whereby the pattern on thephotomask 504 is transferred to the photoresist as a resist pattern(FIG. 5C).

Thereafter, by using the pattern of the photoresist (second layer) 503as an etching mask, the photoresist (first layer) 502 is etched byoxygen reaction ion etching (FIG. 5D). The oxygen reactive ion etchinghas a function of oxidizing Si contained in the photoresist (secondlayer) 503, to increase a resistance to etching of the second layer.

As described above, it becomes possible to transfer various patterns onthe photomask onto the substrate 501, as a resist pattern with a clear(high) contrast.

Embodiment 2

FIG. 6 shows a structure of an optical head in Embodiment 2 of thepresent invention.

In FIG. 6, a slider 602 is held by an arm (not shown) so that it isapart from an optical disk 601, such as a magneto-optical disk, or anoptical disk using fine pits or phase change recording, by apredetermined distance. The predetermined distance is substantially notmore than a size of an opening of a near-field light source. The slider602 is reciprocated by an actuator (not shown) in a predetermined rangeon the optical disk 601. On the slider 602, a near-field probe 603,according to the present invention as a near-field light source, ismounted. The near-field probe 603 is irradiated, though an objectivelens, with light from a semiconductor laser light source, which is notmounted on the slider 602 after being shaped into a collimated beam by acollimator lens. A focus of the objective lens is controlled by a driveactuator, so as to follow with respect to (external) disturbance, suchas a vertical motion of the optical head, depending on an unevenness ofthe medium.

The near-field probe 603 in the present invention comprises a glasssubstrate and a thin metal film 604, provided with a rectangular fineopening 605, disposed on the glass substrate. The rectangular fineopening 605 has an opening size of 80 nm (width)×120 nm (length).Compared with a square fine opening having an opening size of 80 nm×80nm, the rectangular fine opening provides a light intensity, which is1.5 times that of the square fine opening, without substantiallyincreasing a size of a resultant near-field light spot. Accordingly, itis possible to provide an efficient optical head.

A change in reflection characteristic of the optical disk 601 leads to achange in scattering characteristic of near-field light, so that itbecomes possible to read information recorded in the disk as a change inthe amount of light returned to the optical head through the fineopening.

Further, by disposing a magnetic recording head in the neighborhood ofthe optical head, and locally heating a recording medium throughnear-field light energy, it is also possible to provide a light-assistedmagnetic recording head, which facilitates magnetic writing.

The optical head, as a light source, for effecting recording in theoptical disk, can also be utilized as an illumination-mode near-fieldoptical microscope. The optical head, as a light source, for readinginformation from the optical disk can also be utilized as anillumination/light-gathering mode near-field optical microscope. Inthese cases, a near-field optical microscope apparatus is constituted bya sample stage for permitting two-dimensional scanning of a sample bymounting the sample thereon, and a probe-driving system for bringing anear-field light source near to the sample. More specifically, theprobe-driving system includes a cantilever, a piezoelectric actuator,etc., and controls a distance between the near-field light source andthe sample.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it is possibleto provide a method of generating near-field light, capable ofgenerating a higher-intensity near-field light at a high efficiency.Further, it is also possible to provide a near-field exposure mask, anear-field exposure method, a near-field exposure apparatus, and anear-field optical head, which are usable in the near-field lightgenerating method, in combination. It is further possible to provide anear-field optical microscope and a recording and/or reproducingapparatus, which employ the near-field optical head.

1. A near-field light generating method for irradiating light from alight source to a metal film that has a fine opening having a size ofnot more than a wavelength of the light emitted from the light source,and forming a fine light spot adjacent to the fine opening on a lightoutgoing side of the fine opening, said method comprising: providing themetal film with a rectangular fine opening whose length to width ratiois between 1.1 times and 2 times that of a standard square opening,obtained by increasing the length of the standard square opening; andirradiating the metal film with light from the light source to form thefine light spot, which has a length and a width that are substantiallyequal to those of the standard square opening, and wherein the finelight spot has a light intensity, which is not less than two times thatof the standard square opening.
 2. A near-field light generating methodaccording to claim 1, wherein the length to width ratio is about 1.5times that of the standard square opening.
 3. A near-field optical headcomprising: a light blocking film comprised of a metal film; and arectangular fine opening formed in the metal film, the rectangular fineopening having size not more than a wavelength of light emitted from alight source, the light from the light source irradiating the metal filmto form a fine light spot, wherein a length to width ratio of therectangular fine opening is between 1.1 times and 2 times that of astandard square opening, obtained by increasing the length of thestandard square opening, and the fine light spot has a length and widththat are substantially equal to those of the standard square opening,and wherein the fine light spot has a light intensity, which is not lessthan two times that of the standard square opening.
 4. A near-fieldoptical microscope for effecting surface observation of a sample, saidmicroscope comprising: a near-field optical head according to claim 3.5. A recording and reproducing apparatus for effecting recording andreproduction with respect to a recording medium, said apparatuscomprising: a near-field optical head according to claim 3.